\\[-1.8ex] Soil Heterogeneity & $-$0.087$^{**}$ & $-$0.091$^{**}$ & $-$0.066$^{**}$ & $-$0.057$^{**}$ & $-$0.040$^{*}$ & $-$0.053$^{**}$ \\ 
  & (0.044) & (0.042) & (0.034) & (0.027) & (0.022) & (0.021) \\ 
\\[-1.8ex] 
Observations & 23,532 & 23,532 & 23,532 & 23,532 & 23,532 & 23,470 \\ 
R$^{2}$ & 0.007 & 0.258 & 0.414 & 0.519 & 0.529 & 0.540 \\ 
